I know this may be a noobie question, but I'm just trying to learn something new here...

Can someone explain to me the purpose of an underdrive pulley set (other than the lighter weight)? I'm trying to understand how pulleys can increase power.

I appreciate the info!

 

lighter pulley allows it to spin faster?

 

They said something about a "15% underdrive"....how does that translate into power?

 

on the Z, underdriving it is very mild...the gain in engine response comes from the lighter weight vs stock

 

They don't.

The motor turns stuff all the way to the rear tires. If you can delete something like the air conditioning, the more efficient the motor. If you can reduce the weight of anything that must be “driven” by the motor, you increase efficiency.

 

would installing the under drive pulley result in a noticable difference or is this a placebo type mod?

 

from everyone ive asked with this mod whether it be ud or just lt weight, everyone says they have noticed a diff. ive yet to put my AMS lt wt pulley set on due to my lack of time

 

hey i was looking at this kit to install, http://www.thezstore.com/page/TZS/PROD/350z08a/10-2194
what do you guys think?
also whats install like?
and what are the possible downsides to this mod?

 

^ I just installed the non-underdrive set. Included is the crank, idler/stationary, and alternator pulleys. I didn't bother installing the alternator pulley because it would be a major biatch, and the thing is tiny to begin with so it really won't save any weight. The most important one is the crank pulley, and with the right tools, took me maybe an hour to install. Worst part was draining the coolant and taking the upper radiator hose off in order to remove the fans.

If I would buy it again, I would just get the non-underdrive crank pulley. But I got the whole set cheap, so it wasn't a big deal.

 

the unorthodox racing pulleys are good, but buy them from a vendor here on the forums. you can usually get them for that price with the belts included. also the only down side that ive heard of when using these pulleys is that the belts may squeal after the install but this can be taken care of by adjusting the tension. ive also heard that it can make your car harder to get a consistant launch if you are 6mt because the pulley is lighter, almost like the effect of a LT WT flywheel.

 

The theory is right but not sure about real life applicability. Underdrive pullies were popular in 2004 when other performance options were limited. Over the past years they, like grounding kits, have lost considerable interest.

 

So if you had to choose on a stock 2004 ZR Touring, either an exhaust or the UDP which would you choose? I want to change up the sound a bit and know I won't gain a lot with the exhaust. I do need new drive belts and thought I would just replace the rest.

Is the UDP really not worth it anymore. I did this to one of my old cars and it was a great mod to free up some ponies.

 

the pullies are not going to change the sound of the engine

on some cars underdriving makes a bigger difference than on others - the net change is felt by reducing the weight though, so in the case of the Z/G it's really the buyers call which to choose

 

Just installed my WRP Technology UDP on Saturday and I'm liking it.

http://g35driver.com/forums/showthread.php?t=215006

I was shocked when I held the stock and the lightweight pulleys in both hands at just how heavy the stocker is.

Like davidv said, it's reducing the rotational mass of the system, thus helping your engine put more power to the wheels. Similarly, if you had some 20" chrome wheels, or some nice Nismo 18" wheels, your performance would be better with the smaller & Lighter Nismo wheels.